That's one dedicated brother to find his sister a good ****. He would know exactly what she wants, I mean they've foreplayed a ton of times I'm sure. I can't even get grossed out between that because she's so ****ing sexy!

Well.
Say he just drove his sister back from gymnastics, and she's getting in the shower.
He would enter the bathroom once he heard her get into the shower, careful not to make a single sound. As she's soaping up those beautiful tits, Komodo pulls his dick from his sweatpants and starts stroking it. As the whistle song plays and his sister is singing about being a drunken whore and taking it in the ***, Komodo has heard too much and splurges all over his sisters Lacey boyshort panties.
He quickly leaves before he is noticed but not before taking the panties to be framed over his bed for now until eternity.